In general, conductor busbars comprise rigid bars including a conductive path for guiding and for rubbing against a pickup shoe.
Expansion joints need to be provided in order to ensure both electrical continuity (for electrical pickup) and mechanical continuity (for guidance). Such expansion joints are provided at the free ends of two adjacent bars, which ends make contact with each other in order to ensure electrical pickup continuity regardless of their relative longitudinal position. This may be done by providing a notch in the side of the conductor bar up to the middle of its conductor track in order to have two half-bars overlapping each other side-by-side, or, better still, the free ends of adjacent bars may have complementary systems of interfitting plates in the form of two combs. As a result, each plate at the free end of a bar is in contact with one or two adjacent plates on the free end of the other bar in a central region of the expansion joint.
Such expansion joints pose both mechanical and electrical problems. The bars must be kept in alignment, and electrical continuity between the bars must be ensured in addition to ensuring electrical pickup continuity.
It is conventional to provide a mechanical guidance fitting on the side of the rigid bars which is opposite to the conductor track, which fitting interconnects the two adjacent bars on either side of the expansion joint in such a manner as to enable relative longitudinal sliding to take place therebetween while keeping said bars in alignment. The presence of such fittings is a drawback, particularly in relation to factory assembly time.
A flexible link cable or braid is conventionally used to provide electrical continuity between the bars. This has the advantage of simplicity, however when high currents are to be passed (e.g. 1,600 amps) this requires a flexible cable or braid of considerable size, which is incompatible with a compact installation. In addition, placing such flexible braids or cables on the sides of the bars, as is conventional, leads to additional safety precautions being necessary, in particular if the equipment is to operate out of doors in wet weather.
A first aim of the present invention is to provide a novel electrical connection device which is more reliable and which provides higher performance than existing devices, which novel device should be capable of withstanding high currents regardless of the relative longitudinal position of the adjacent bars on either side of an expansion joint.
Another aim of the invention is to maintain bar alignment in order to avoid the expansion joint being damaged when interfitting plates are used whose shoe-rubbing edges constitute extensions of the conductor paths over the entire length of the expansion joint.
Another aim of the invention is to simplify the design of conductor bars in order to reduce factory assembly time, thereby enabling very long bars to be made ready for fitting at a reasonable production cost.